1. Field of the Invention
The present invention relates broadly to refrigerated showcases, particularly open-fronted display and storage cases with air curtains. More specifically, the present invention relates to a refrigerated showcase having an opening through which a consumer can view and access stored items on display and to such a showcase wherein cooling air is introduced through a perforated interior panel with the coolant air maintained within the refrigerated compartment by an air curtain passed downwardly within the showcase opening.
2. Description of the Related Art
An example of this type of showcase is described in U.S. Pat. No. 3,696,630 granted on Oct. 10, 1972, to Bressickello who discloses various self-service showcases constructed with front access openings for the purpose of displaying comestibles such as meat, eggs and vegetables. In such showcases, the cooling system includes a refrigerant coil, also known as an evaporator coil, which is located in such position so as to cool air circulating through the showcase.
The refrigerant coil is sometimes oriented above a relatively small drip pan, also referred to as a dissipater pan situated in a location so as to collect condensation from the coil. When the water level rises to a predetermined level, this condition is sensed and a pump is activated to lift the water to an overhead dissipater pan arranged on top of the showcase. The dissipater pan may include a heating coil to dissipate any accumulated water. Other showcases eliminate condensation from the refrigerant coils by a drainage system that communicates with a floor sink.
An example of a showcase of the type where condensation from the evaporator coil is pumped to a dissipater pan arranged on top of a cabinet of the refrigerated showcase is illustrated in U.S. Pat. No. 4,766,737 granted on August, 1988, to Baxter, II. In this prior art device, a high temperature coil of the condenser assembly is associated with the lowermost of an array of dissipater pans in order to effect the transfer of heat to the condensate which has been pumped up to the dissipater array atop the cabinet of the refrigerated showcase.
The open-fronted, refrigerated showcases with air curtains in the prior art have reached a level of efficiency such that additional improvements are not readily achieved.
It is well known in the prior art to use perforated wall dividers and/or rear panels which are angled to form an air plenum in association with the back of the showcase. These air plenums are shaped to have a decreasing volume through which cooled air is passed upwardly with the flow also passing through perforations in the wall dividers into the refrigerated showcase. This feature is illustrated in U.S. Pat. No. 3,696,630 previously mentioned and in U.S. Pat. No. 5,345,778 issued on Sep. 13, 1994, to Roberts.
It is also known to route cooled air to a bottom portion of cooling compartments where foodstuffs are stored. Bottom storage bins, where foodstuffs are placed to replenish the display shelves located above the storage area, are commonplace. However, cooling the storage area is difficult to do. Prior art devices have cooled the storage are by diverting a portion of the cooled air which is flowing upwardly from housings in which evaporator coils and air-moving fans are arranged. An example of such an arrangement is found in U.S. Pat. No. 5,345,778 just mentioned.
In accordance with the present invention, three methods of improving air curtains in open-fronted refrigerated showcases have been incorporated in the refrigerated compartment, in the refrigerant system atop the cabinet, and in the air circulation system.
As shall be fully explained below, one purpose of the present invention is to achieve optimal heat exchange by continuously trapping particles suspended in the air that flows into the components of the refrigerant system which over time becomes fouled and impedes air flow and/or the efficiency of the heat exchange. In particular, an air filter is used atop the showcase. This air filter and precondenser coils, situated beneath the air filter, are both exposed and susceptible to fouling. Advantageously, these elements of the present refrigeration system are cleaned by condensate originating at the evaporator coils. This condensate is pumped from a lower drip pan up to the top of the showcase, then expelled over the air filter. The condensate then travels from the air filter over the precondenser coil into the dissipater pan. The precondenser coil, preferably made of copper tubing, is inserted between the compressor and the condenser coil. As the refrigeration gas is sucked from the evaporator coil, the compressor places the gas under a higher pressure, thus raising the gas temperature. The hot gas is then pushed into the precondenser coil which has a sufficient length to evaporate the water that lands in the dissipater pan. The lengthy copper tubing coil between the compressor and the condenser coil functions to evaporate the water which has collected during the operation of the refrigerated showcase. The precondenser coil is situated in the dissipater pan, suitably resting on the bottom of the pan, with at least a portion of the coil exposed to the atmosphere in the open section of the top of the showcase. The precondenser coil also sits forward of the face of the air filter. Preferably, a major portion of the precondenser coil is exposed to the atmosphere. The precondenser coil also assists the condenser coil by precondensing the refrigerant. The air is pulled through the space where the filter, precondenser and dissipater pan is located. The air then circulates outside the precondenser coil and acts as a heat exchange medium. Precondensing refrigerant gas into liquid, moreover, makes the condensing system more efficient.
Another aspect of the present invention, as shall also be further explained below, is to minimize coolant air loss through the showcase opening. This advantage is achieved by a method of identifying, measuring, and ameliorating coolant air loss by providing a lip along vertical sides of the opening in the refrigerated compartment. The lips extend vertically along at least a portion of each of the two vertical sides of the opening where, as it has been discovered, the loss of cooled air from the refrigerated compartment is greatest.
The present invention also provides an apparatus for assuring proper cooling at the bottom of the refrigerated compartment of the showcase.
A further aspect of the present invention relates to the use of an air divider and plenum arrangement which directs the coolant air through perforations in the back of the refrigerated compartment so that the coolant air flows over foodstuffs which are stored at the bottom of the refrigerated compartment in an area beneath the lowermost display shelf. In other words, a diverter and plenum arrangement is utilized to achieve routing of the coolant air to the bottom of the refrigerated compartment below the lowermost display shelf in a facile manner.
It has also been found that, in refrigerated showcases wherein there is an opening in the front thereof through which a consumer can view and access foodstuffs on display, these foodstuffs in the showcase are cooled by cold air introduced from a perforated panel. Such refrigerated showcases include an air curtain generated within and directed downwardly from the top of the opening. After a determination of the flow rate, the loss of coolant air through the air curtain can be either reduced or prevented altogether by using lips that extend from the vertical edges partially into the opening.
The following method can be used to determine the dimensions of the lips that limit coolant air loss through the air curtain. In open-fronted, refrigerated showcases, a 4xe2x80x3 lip on each side has been found suitable to minimize the coolant air loss along the vertical edges of any refrigerated compartment which has an opening of about 56xe2x80x3 in height. The method of determining the size of the lips needed for the vertical edges involves several steps.
First, load the refrigerator shelves with the product to be refrigerated and displayed, preferably at a desirable product temperature sufficient to avoid the possibility of spoilage. Actually, this step can be omitted, but it is preferred to use a stocked compartment.
Second, adjust the rate of flow of the coolant air to obtain a stable air curtain. This step is achieved by producing a nominal air flow of 500 cubic feet per minute by four pans which are each rated at 125 cubic feet per minute so that an actual air flow rate of about 330 cubic feet per minute is obtained.
Third, introduce a visible additive, such as artificial smoke to the circulating air in order to enable observation and identification of any air escaping at the periphery of the front opening.
Fourth, apply a first lip extending from one vertical side edge into the opening and a second lip extending from another opposite vertical side edge into the same opening.
Fifth, observe, by increasing and/or decreasing, the extension of the lips into both side edges of the opening. When the escape of air through the air curtain is minimized at the vertical periphery of the opening in the refrigerated showcase, the optimal lip size has been empirically determined.
The lips are then affixed to the vertical side edges which extend into the opening in the showcase a distance based on the observations made in order to limit the loss of coolant air through the air curtain.
Thus, in accordance with the present invention, the loss of coolant air through the air which is passed over the displayed products is minimized. The coolant air then emerges from the refrigerated compartment for recycling with the circulating air forming the air curtain at the opening in the showcase. As heretofore noted, the optimum conditions for operation and determination of lip size are identified empirically by observing and adjusting the size of the lips which minimize the loss of coolant air at the vertical peripheries of the opening in the refrigerated compartment.
Furthermore, the controlled flow of coolant air through perforated openings in the panel is facilitated by an air divider and plenum arrangement that provides for adequate contribution of the coolant air the food storage area which is located at the bottom of the refrigerated compartment, typically beneath the first storage shelf. As air is ejected upwardly by the four fans in the fan housing, the air is pushed between the back wall which is plumbed straight and the perforated panel which is inclined slightly backwards by approximately six degrees from its vertical axis. The perforated panel has at its lower end the air divider and plenum arrangement situated beneath the first display shelf. The air divider and the plenum arrangement are installed to force air flow through the perforated panel into the bottom storage section of the refrigerated compartment. Thus, air flow equilibrium throughout the perforated panel, including the bottom storage section of the refrigerated compartment, is accomplished. This equilibrium is achieved by forcing air to be approximately the same amount in all spaces where the products are placed. The reason for this result is believed to be that the air travels fastest when it is nearest to the fans, so that the air travels to the upper part of the panel and crosses through the perforations with great ease.
The multiple fans, which move cooled air over the evaporator coils situated in the bottom of the refrigerated compartment, reduce condensation on the evaporator coils that are used to cool the air circulating in the showcase so that icing is reduced on the evaporator coils.
Water collecting on the evaporator coils is captured in an evaporation tray situated below the evaporator coils and is pumped to the top of the showcase where the condenser is located. At the top, the water sequentially is passed over a filter which functions as a water evaporator and also functions to remove particulate matter and other foulants, whereby the water from the evaporator coils functions both to clean the filter and to cool the air passing through the filter before the air contacts the condenser coils of the refrigeration system. The water runs from the filter to the dissipater pan and then to the precondenser coils carrying refrigerant from the compressor. These precondenser coils are thus cooled by cold water originating at the evaporator coils. The filtered air passing over the condenser coils, which air is further cooled before contact by the water, passes over and/or through the filter before absorbing heat produced during refrigerant condensation. At the same time, the rate of evaporation from the dissipater pan lying under the precondenser coils is substantially increased and the risk of water overflow is minimized. The heat generated during compression is exchanged through both the condenser coils and the precondenser coils which comprise another set of coils located downstream of the condenser coils. The precondenser coils in essence function as heating coils to assist in the evaporation of water from the dissipater pan using the heat of condensation, thereby providing two desirable fictions using energy available within the refrigeration system itself, namely removing heat from the compressed refrigerant and adding heat to the condensate which accumulates in the dissipater pan.
Furthermore, the present invention relates to a self-service refrigerated showcase having therein an enclosure for the display of cooled foodstuffs. The enclosure has a front access opening defined by top, side, and bottom housing panels. At its sides, the enclosure is defined by vertically elongated strips corresponding to the side housing panels. This enclosure provides access to the foodstuffs on display.
Also, the enclosure has other advantageous features. For example, there is a perforated panel through which coolant air is introduced and passed over the foodstuffs. Also, there is a top panel having near to the forward part thereof a structure for forming an air curtain which moves coolant air downwardly within the front access opening after diverting the coolant air from the perforated panel. This coolant air originated from a space behind the perforated panel before reaching the access opening.
In accordance with the present invention, a structure is provided for minimizing air loss through the front access opening. This structure is a lip extending from each of the housing side walls along at least a portion of the length of the opening. In this way, coolant air loss which has been observed to occur predominately at the vertical periphery of the opening is substantially prevented.